System and method for role based analysis and access control

ABSTRACT

A system and method for program access control includes, for a typestate, providing typestate properties and assigning a role to the typestate in a program in accordance with the typestate properties. Access to operations is limited for the typestate in the program based on the role assigned to the typestate and an access permission level.

RELATED APPLICATION INFORMATION

This application is a Continuation application of co-pending U.S. patentapplication Ser. No. 11/446,104 filed on Jun. 1, 2006, which isincorporated by reference herein in its entirety.

BACKGROUND

1. Technical Field

The present invention relates to access control of programs and moreparticularly to systems and methods for role based security and rolebased security analysis.

2. Description of the Related Art

In Java 2 Enterprise Edition™ (J2EE™) and MICROSOFT™, XML Web Servicesplatform (.NET™) roles are assigned to methods using externalconfiguration files, called the deployment descriptors. The securitymodel of J2EE™ and .NET™ are quite similar, and for simplicity examplesherein will employ the Java™ programming language. J2EE™ and the Java™programming language are trademarks of SUN MICROSYSTEMS™. .NET™ is atrademark of the MICROSOFT CORPORATION™.

Assigning roles to methods, although conceptually simple, in practice isquite complicated. For instance, in order for a deployer to assign arole r to a method m, the deployer must understand the set of roles Rthat are assigned to each method n that can be invoked directly orindirectly from m, and that r has to be “consistently” assigned withrespect R. Understanding such role consistency is a non-trivial task.Also, in J2EE™ roles are defined with respect to method access and notdata access. Therefore, in order to protect sensitive data, one has toencode data access control using method access control. This can lead tointeresting and subtle access control problems when accessing sensitivedata, including information leakage through data flow from one method toanother.

SUMMARY

A system and method for program access control includes, for atypestate, providing typestate properties and assigning a role to thetypestate in a program in accordance with the typestate properties.Access to operations is limited for the typestate in the program basedon the role assigned to the typestate and an access permission level.

These and other objects, features and advantages will become apparentfrom the following detailed description of illustrative embodimentsthereof, which is to be read in connection with the accompanyingdrawings.

BRIEF DESCRIPTION OF DRAWINGS

The disclosure will provide details in the following description ofpreferred embodiments with reference to the following figures wherein:

FIG. 1 is an illustrative observer pattern program used as an examplefor demonstrating present principles;

FIG. 2 illustratively shows code for role definitions in accordance withan illustrative embodiment;

FIG. 3 is a call graph for the program depicted in FIG. 1;

FIG. 4 is an illustrative pointer graph for the program depicted in FIG.1;

FIG. 5 is an application model showing entry methods and roleassignments in accordance with an illustrative example;

FIG. 6 is an annotated call graph showing Role_(i) and Role⁺ roleassignments for each method in accordance with one illustrativeembodiment;

FIG. 7 is a typestate diagram for a File program operation in accordancewith an illustrative example;

FIG. 8 is a hierarchical typestate diagram for the diagram of FIG. 7;

FIG. 9 is a diagram showing a role hierarchy assignment in accordancewith an illustrative embodiment;

FIG. 10 is a block/flow diagram showing a system/method for accesscontrol using typestate role assignments in accordance with oneembodiment;

FIG. 11 is a block/flow diagram showing a system/method for analyzingrole consistency for program access control in accordance withillustrative embodiments; and

FIG. 12 is a block diagram showing an illustrative system for employingrole based analysis and access control in accordance with anillustrative embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A data-centric security system and method are presented, which includeat least the following two concepts. 1) Role Analysis: A simpleinterprocedural static analysis for detecting security problems whenobjects are accessed by multiple methods that do not have compatible orconsistent assignment of roles is provided. Then, a notion of an object“escaping” a role is presented, and a simple interprocedural staticanalysis for computing the set of objects that may escape a role isprovided.

2) Consistency-Based Security and Role Typestates: J2EE™ method-basedrole assignment is extended to consistency-based role assignment. Onefocus includes assigning roles to typestates rather than methods.

Role Based Access Control (RBAC) is a popular mechanism for defining andmanaging access to security sensitive resources. In RBAC, securityproperties, such as access control to sensitive resources, arecontrolled through roles. Users are assigned one or more roles, who theninherit the security properties associated with the roles. RBAC providesgreater security by preventing users from obtaining inconsistent orincompatible security properties. J2EE™ and .NET™ support RBAC byrestricting the roles to method access. In J2EE™, a role r is simply anamed set of methods M, and whenever a principal P is assigned the roler the principal can then access any of the methods in M. In practiceonly application entry methods are assigned roles.

In J2EE™, there are two ways to specify access control security: (1)declarative or container security and (2) programmatic or applicationsecurity. In container security, access control to sensitive resourcesis defined in an external configuration file, as part of a deploymentdescriptor. The container then manages the access control to sensitiveresources. In application security, access controls are encoded withinthe application and the application directly manages the access controlto sensitive resources. The J2EE™ framework encourages the use ofdeclarative security since it enables greater flexibility by separatingsecurity properties from the application logic. Declarative securitywill illustratively be employed in describing embodiments of the presentinvention. Further description will follow on systems and methods whichemploy these aspects and features.

Embodiments of the present invention can take the form of an entirelyhardware embodiment, an entirely software embodiment or an embodimentincluding both hardware and software elements. In a preferredembodiment, the present invention is implemented in software, whichincludes but is not limited to firmware, resident software, microcode,etc.

Furthermore, the present invention can take the form of a computerprogram product accessible from a computer-usable or computer-readablemedium providing program code for use by or in connection with acomputer or any instruction execution system. For the purposes of thisdescription, a computer-usable or computer readable medium can be anyapparatus that may include, store, communicate, propagate, or transportthe program for use by or in connection with the instruction executionsystem, apparatus, or device. The medium can be an electronic, magnetic,optical, electromagnetic, infrared, or semiconductor system (orapparatus or device) or a propagation medium. Examples of acomputer-readable medium include a semiconductor or solid state memory,magnetic tape, a removable computer diskette, a random access memory(RAM), a read-only memory (ROM), a rigid magnetic disk and an opticaldisk. Current examples of optical disks include compact disk-read onlymemory (CD-ROM), compact disk-read/write (CD-R/W) and DVD.

A data processing system suitable for storing and/or executing programcode may include at least one processor coupled directly or indirectlyto memory elements through a system bus. The memory elements can includelocal memory employed during actual execution of the program code, bulkstorage, and cache memories which provide temporary storage of at leastsome program code to reduce the number of times code is retrieved frombulk storage during execution. Input/output or I/O devices (includingbut not limited to keyboards, displays, pointing devices, etc.) may becoupled to the system either directly or through intervening I/Ocontrollers.

Network adapters may also be coupled to the system to enable the dataprocessing system to become coupled to other data processing systems orremote printers or storage devices through intervening private or publicnetworks. Modems, cable modem and Ethernet cards are just a few of thecurrently available types of network adapters.

Referring now to the drawings in which like numerals represent the sameor similar elements and initially to FIG. 1, to illustrate how securityroles are defined in J2EE™, an example application of an ObserverPattern 10 is illustratively shown. The Observer Pattern 10 is made oftwo entities: (1) a subject that includes data of interest (see e.g.,ISubject in FIG. 1) and (2) one or more observers (IObserver in FIG. 1)that display the data of interest. The Observer Pattern 10 defines aone-to-many dependency between the subject and the set of observers.Whenever the data in the subject is updated, all the observers that havebeen registered with the subject for the data are notified of theupdate.

In J2EE™ the security roles are defined within an assembly descriptor asshown below:

<assembly-description> <security-role>   <role-name> Manager</role-name>   <role-name> Notifier </role-name>   <role-name> Director</role-name>   <role-name> DisplayId </role-name>   <role-name>DisplayName </role-name>  </security-role> </assembly-description>

Once the security roles are defined, the application deployer thenassociates each role with a set of methods.

Referring to FIG. 2, how roles are defined as a set of methodpermissions is illustratively shown. As can be seen in FIG. 2, roles mayinclude, e.g., a Notifier, a Manager, a Director, DisplayID andDisplayName. For example, the Notifier role has the permission to invokethe method setData defined in the Subject class.

In J2EE™ roles are typically defined for enterprise Java™ beans (EJB)components rather than arbitrary classes. For simplicity, examples ofgeneral Java™ classes will be employed, instead of EJB examples. For theexample shown in FIG. 2, a principal with the Notifier role is permittedto access (that is, invoke) the method setData that is defined in theclass Subject. Similarly, a principal with the DisplayId role ispermitted to access all the methods (denoted by the “*” operator) thatare defined in the class ObsId.

In J2EE™ one can use such access control specifications for other Webresources such as access to a HTTP method on a URI (Universal ResourceIdentifier). Also, methods that are not part of any role, are permittedto be accessed by any principal.

Consider a principal “Mark” who is authorized with the role DisplayId.It may be assumed that an authentication mechanism similar to a J2EE™authentication mechanism may be employed as in known in the art.Further, assume that Mark invokes a method Driver.main. Since thismethod is not part of any role, an access control manager does notprevent Mark from executing the method. Now when “Mark” attempts toinvoke Subject.addObs (indirectly through Drive.main), a securityexception will be thrown since Mark does not have either the Directorrole or the Manager role. At this point, an application deployer mayassign the Director role to Mark so as to avoid an access controlexception, which in turn may violate the principle of least privilege.Essentially this means that to associate a role r to a method m, anapplication deployer has to understand the set of methods S that can bedirectly or indirectly invoked by m.

Understanding such control flow is not a trivial task, especially by anapplication deployer. In the J2EE™ security model as known to thoseskilled in the art, one can also delegate permissions by associating the<run-as> tag to a class C in the deployment descriptor. The effect ofsuch an association is to grant the permission of C to all methods thatcan be directly or indirectly invoked from C. A careless run-asdelegation can introduce some interesting and unforeseen permissionproblems.

One main problem with role based access control (RBAC) in J₂EE™ is thatroles are defined for controlling access to methods and not forexplicitly controlling access to data. In other words, there is noexplicit mechanism for controlling access to data fields and objectinstances.

Access control to data and objects has to be performed implicitly bygiving access to methods which in turn accesses the data. An importantsecurity implication of such access control through methods is thatinformation could potentially be leaked through data flow acrossmethods.

Referring again to the example in FIG. 1, using pointer analysis, onecan determine that the object referenced in statement 43: is accessed bymore than one method (e.g., Subject.notifyObs, Subject.addObs, andObsId.update). Unless the roles are assigned correctly or consistentlyamong these methods, there could be potential access control andinformation flow security problems.

Referring again to FIG. 2, the method ObsName.update and the methodObsId.update are part of two different roles. Therefore, whenobs.update( ) is invoked at statement 43: the target method could beeither ObsId.update or ObsName.update depending on the runtime type ofobs. Since, ObsName.update and ObsId.update have two different roles,there could be a potential security problem when the method isdispatched. Therefore, it is important to ensure that both methods areassigned the same role. The security problems that arise are either: (1)too many permissions are given to a principal, which in turn may violatethe principle of least privilege, or (2) inadequate permissions aregiven, which can lead to unnecessary access control exceptions. Therecan be subtle security violations, such as information tainting andinformation leakage, when the principle of least privilege iscompromised. Note that a simple propagation of roles over the call graphof the program is not sufficient to detect such data flow securityproblems.

Aspects of the present embodiments focus on data-centric security byintroducing two concepts: (1) Role Analysis and (2) Consistency-BasedSecurity and Role Typestates.

(1) Role Analysis: A simple interprocedural static analysis fordetecting security problems that may arise when objects are accessed bymultiple methods that do not have compatible or consistent assignment ofroles to methods is provided. The notion of an object “escaping” a roleis presented and a simple interprocedural static analysis for computingthe set of objects that may escape a role is described.

(2) Consistency-Eased Security and Role Typestates: Method-based roleassignments are extended to consistency-based role assignments and rolesare assigned to typestates rather than methods. The typestatedescription of a class is a configuration of its fields, and essentiallyabstract consistency properties of the fields.

RBAC Models and Program Representation: Static analysis is a process fordetermining the relevant properties of a program without actuallyexecuting the program. A program includes a collection of methods orprocedures and is represented using a call graph (CG). A CG G=(N, E) isa directed graph, where N is a set of nodes and E is a set of edges. Theset of nodes N is partitioned into two disjoint sets: (1) N_(c) is a setof call site nodes and (2) N_(m) is a set of method nodes. The set ofedges E is also partitioned into two disjoint sets: (1) E_(m,c) is a setof edges from a method node x_(m) to each call site node x_(c) definedin the method, and (2) E_(c,m) is a set of edges from a call site nodex_(c) to each method node x_(m) that can possibly be invoked from thecall site x_(c). A path is a sequence of edges starting from some nodein the call graph. If there is a path from a method node x_(m) toanother method node y_(m) then the method corresponding to x_(m) maydirectly or indirectly invoke the method corresponding to y_(m).

Referring to FIG. 3, a call graph 200 is illustratively shown for theexample program of FIG. 1, where numbers in FIG. 3 correspond tostatement numbers in FIG. 1. Pointer analysis includes computingpoints-to information, represented as a pointer graph, at relevantprogram points. A pointer graph includes a set of nodes representingcompile-time objects and pointer references. For heap allocated objects,pointer p can point-to an object O if p can include the address of O.Typically, the address of O is not known at compile-time and one thenassigns compile-time labels to heap objects. There are several differentkinds of pointer analyses depending on precision and cost of theanalysis. Typically, flow insensitive and context insensitive analysistends to be cheaper, but less precise than flow sensitive and contextsensitive analysis.

Referring to FIG. 4, a pointer graph is illustrated that is computedusing a flow insensitive pointer analysis for the code of FIG. 1, wherenon-bracketed numbers in FIG. 4 correspond to statement numbers inFIG. 1. The notation p->O may be employed to denote that p points-to O.It will also be assumed that objects have fields and each field has aname that can be accessed from the object type or class. Dot-notation isused to access fields, e.g., p.f or O.f, and it can be stated that:p.f->O to denote that p points to some object O₁ and the field f of O₁points to another object O.

Role Modeling: J2EE™ security is defined in terms of: (1) principals orauthenticated users, (2) roles that define named job functions, and (3)permissions that map a role to a set of operations or methods defined inone or more classes. In J2EE™, roles are often defined for EnterpriseJavaBeans (EJBs), and for simplicity, herein, Java™ classes will beemployed instead of EJBs. For instance, consider the Subject class thatincludes the methods setData, addObs, removeObs, and notifyObs. A rolesuch as Notifier (see FIG. 2) is given permission to invoke setData. Onthe other hand, a role such as Director is given permission to invokeall four operations. Notice that a principal with a Director role caninvoke any operation that a principal with a Manager role or a Notifierrole can invoke. In other words, Director is considered to be “senior”to Manager and Notifier.

Let C denote a set of classes for which RBAC is provided, and let Mdenote a set of methods in C. A permission Per is a mapping from role rin R to a subset of methods in M. Now, let Per(r) denote the set ofmethod permissions assigned to a role r. For example,Per(Manager)={Subject.addObs, Subject.removeObs}.

Definition [Senior Roles]. Let r and s be any two roles in R. r is asenior role of s, denoted as r

s, if Per(r)

Per(s).

Conversely, a junior role may be defined as follows. r

s, if Per(r)

Per(s).

Next, a role graph is defined in which nodes represent roles and edgesrepresent the senior (junior) relations. The role graph form employed inthis disclosure will include a lattice structure, with

representing a role that is the union of all method permissions and

representing a role whose permission set is the empty set. A lattice isa partial order with a join and a meet for every pair of nodes. Givenany two nodes x and y, the set union of x and y is the join (

), and the set intersection of x and y is the meet (

).

Now let Per_(i)(r) be a set of method permission that is initiallyassigned a role r (as specified in the deployment descriptor). In J2EE™a method permission can be assigned to more than one role. LetRole_(i)(m) denote the set of roles that an application deployerinitially assigns to m. In other words, Role_(i)(m)={r|mεPer_(i)(r)}.For example, Role_(i)(Subject.setData)={Notifier, Director}. If a methodis not explicitly assigned to any role, then it can be accessed by anyprincipal. Note that one can also use the “*” to indicate all themethods in a class as belonging to a specific role.

Role Analysis: Two illustrative role analyses are presented and include:(1) role consistency analysis for computing consistent role assignmentand (2) role escape analysis for computing the set of objects that mayescape a role.

Role Consistency Analysis: Let r be a role assigned to m (by anapplication deployer), and let m′ be a method that can be invokeddirectly or indirectly from m. A principal who is assigned the role rshould also have permission to invoke the method m′, i.e., m′ shouldalso be in Per(r). Often an application deployer handles only entrymethods of an application or a component. These entry methods areessentially the application programming interface (API) of theapplication. In the case of a Java™ application, the entry methods arethe set of public and protected methods defined in interfaces andclasses. Therefore, an application deployer has the capability to definepermission sets and assign roles based on the entry methods defined inan API.

Let A be an application, let M_(e) be a set of entry methods to A (asdefined in its API), and R be the set of roles defined using the entrymethods.

Referring to FIG. 5, an application or component model is illustrativelyshown. Notice that an entry method such as m1 can directly or indirectlyinvoke another entry method m2. One question is how to define consistentroles and permission sets that are based on only the entry methods of anapplication. Consider an entry method m1εM_(e) and let r₁εR. Now, definer₁ to include m1 in its permission set, that is m1εPer(r₁), andtherefore r₁εRole(m1). What this essentially means is that if aprincipal P is assigned the r₁, then P has the permission to invoke m1.Now let m2 be some other method reachable from m1, and so P should alsohave the permission to invoke m2. Let Per(r₂)={m2, m3}, and som2εRole(r₂). r₁ and r₂ should be ensured to have a consistent permissionset.

There are two cases to consider: (1) m2 is not in Per(r₁) and in thiscase P should also be assigned the role r₂ so as to avoid access controlexception. On one hand, by assigning r₂ to P, also give P the permissionto access m3, which violates the principle of least privilege. On theother hand, m3 may be in a different sub-component, in which caseseparating the roles makes sense in some situations, even if theprinciple of least privilege is violated. (2) m2 is in Per(r₁), and inthis case the assignment is consistent.

One way to compute consistent role assignment is to first determine theset of methods that are reachable from an entry point in the call graphof the program. Let L be the set of methods that are reachable from anentry point mεM_(e) in the call graph. Let L′_(m)=L∩M_(e), and so L′_(m)is a set of methods that are reachable from m and the set of methods arealso entry methods. Now let r be a role with mεPer(r) Since a methodl′εL′_(m) is also reachable from m, ensure that l′εPer(r). So ratherthan defining arbitrary roles and permission set, a deployer firstcomputes L′_(m) for each entry method m. The deployer can then defineroles based on the entry method m and L′_(m) by ensuring that L′_(m)

 Role(m).

Applications may be composed of many components and the components areassigned with consistent roles. Consider the example shown in FIG. 1 andthe role assignment shown in FIG. 2. Let Role_(i) denote the initial setof role assignments. In order for a principal to invoke Subject.setDatathe principal not only needs the Notifier, but also DisplayId andDisplayName roles.

Referring to FIG. 6, an annotated call graph is illustratively shownwith Role_(i) and Role⁺, which are the initial role assignments and theminimum roles needed to invoke the methods. Computing Role⁺ for eachmethod is a straightforward backward propagation of roles over the callgraph and at each step only propagation of junior roles up the callgraph is performed. That is, a lattice join is performed at each stepand the joined role information is propagated.

The role analysis described previously is preferably based onreachability over a call graph of a program. Although role propagationover the call graph may be important in preventing certain kinds ofaccess control problems, it does not detect access problems that couldhappen due to data flow across methods. A limitation of the J2EE™security model is that it focuses on securing the mechanism (that is,methods) that access sensitive information or resources. For instance,J2EE™ does not allow one to specify roles for class fields and classinstances. Subtle problems may arise due to data flow across methods.For example, the receiver expression (such as 43: obs.update(data) inFIG. 1 can target more than one method. Programmers have to make surethat the roles assigned to the target method are consistent with therole assigned to a method that invokes the object.

Also, an object is often accessed by multiple methods that havedifferent roles assigned to them. Consider the points-to graph shown inFIG. 4, and, in particular, the object 62:ObsId. This object is directlyaccessed by the methods Driver.main (which created the object),ObsId.update (via the “this” parameter), and Subject.notifyObs. Now,consider the role assignment and method permission shown in FIG. 6. Themethod ObsId.update is assigned only to role Display. Unfortunately,since the object, 62:ObsId, is also accessed by other methods, there canbe inconsistencies among roles assigned to different methods that accessthe same object. This can lead to information leakage.

Given the pointer graph of a program, for each object, the set ofmethods are computed that directly access the object. Call the resultinggraph a method-annotated pointer graph (MAPG). It is straightforward tocompute this information if fully qualified names are used forreference. Consider the pointer graph shown in FIG. 4 and the object62:ObsId. The set of methods that access this object can be read offfrom the pointer graph, which is Driver.main, Subject.addObs,Subject.notify, and ObsId.update. Since any of these methods have the“capability” to access the object, the object is assigned a role that isthe least upper bound of the roles assigned to these methods. Now aprincipal who wants to access the object referenced by 62:ObsId shouldhave a role that is at least equal to the least upper bound of the rolesassigned to the methods that access the object. Unfortunately, in J2EE™,it is not possible to assign roles to objects or class instances.

Role Escape Analysis: The concept of role escape analysis will now bedescribed in accordance with present principles. Escape analysis is aprocedure for determining the set of objects that escape the life timeof a method or a thread. Consider the following simple example:

1: void foo( )  { 2:  LinkedList head  = new LinkedList( )  ; 3: bar(head)  ; 4:  } 5: void bar(LinkedList h){ 6:   LinkedList n = newLinkedList( )  ; 7:   n.next = null  ; 8:   h.next = n  ; 9:  }

The object 6:bar.LinkedList created at 6: escapes the method bar becausethere is an access path to the object from the parameter reference h. Onthe other hand, the object 2:foo.LinkedList created at 2: and the object6:bar.LinkedList created at 6: do not escape foo. One simple way tocompute whether an object O escapes a method M is first to construct thepointer graph and then check if there is a path to O in the graph thatcan be reached by some node O′ that is accessed in some other method Mland the life time of M′ that exceeds the life time of M.

In role escape analysis, the method escape analysis may be extended asfollows. An object O role escapes a method M with role R if there is apath in the pointer graph from some node O′ that is accessed in someother method M′ with role R′ and R

 R′. Conversely, an object O is role confined to a M if O does not roleescape M. A definition of role escape employed herein is more generalthan the traditional method or thread escape, whereby method lifetime isdefined herein as a role. The role escape analysis essentially includesdetermining if a node p in the pointer graph that is annotated withmethod m and role rεRole⁺(m) is reachable from another node p′ that isannotated with m′ and role r′εRole⁺(m′) and r

 r′.

Notice that the converse of role escape, which is role confinement, ofan object is closely related to information flow security. Since rolesare modeled using a lattice structure, if an object O does not escape arole R then the object cannot leak information outside the role. Also,if an object escapes a role, the object can become “tainted” by anexternal principal with access to the object.

Consistency-Based Security: It is often the case that an applicationdeveloper has a better understanding of the application that he or sheis developing than an application deployer or the system administrator.On the other hand an application deployer has a better understanding ofthe application deployment environment than an application developer.One idea behind consistency-based security (CBS) is to focus on theconsistency properties of data and methods. An application developersimply identifies and defines the consistency properties as codeannotation. A simple consistency property could be that two fields of aJava™ class are modified by the same set of methods. Another consistencyproperty is the typestate property, which is often used to specifyordering of methods in an application. In CBS, a tool can scan the codeand present the developer's consistency properties to an applicationdeployer. An application deployer can then use the consistencyproperties as a guide for associating security properties to roles, andthen grant authorization to users.

Data Consistency Security: a simple consistency property in which two ormore fields of an object are all accessed by the same set of methods.Given this property, an application deployer can then associate the samerole for all methods that access these fields. Consider a simpleemployee record in a company.

Employee Record:

enum EmpType =  {RSM, Manager, SoftEng, Staff}  ; class Employee  {  String fname ; // first name   String lname ; // last name ;   int id;     // company identity number   int ssn ;    // social securitynumber   String gender ;   String ethnic ; // ethnicity   EmpType etype; }

Suppose an application developer is developing a business application,such as a payroll application, and decides that gender, and ethnicity(“ethnic”) have the same “consistency property. A simple example of aconsistency property is that the two fields are always accessed by thesame set of methods. Another example of a consistency property is accessrights; if a user is permitted to access one of the two data fields,then the user is automatically allowed to access the other data field.Yet another example of a consistency property is encryption; the valuesof the two data fields should use the same encryption/decryption keys.An application developer usually has a better understanding of theconsistency properties than the application deployer. For instance, ifgender, and ethnic are always accessed by the same set of methods, thedeveloper can then define a simple consistency property classificationcalled race.

Consistency Property Classification—Race:

class Employee {   access(name, idy)  String fname ;   access(name, idy) String lname ;   access(idy)     int id ;   access(idy)     int ssn ;  access(race) String gender ;   access(race) String ethnic ; }

Often a field (or a method) can belong to more than one class of aconsistency property. For instance, fname (first name) and lname (lastname) belong to two different classes of the access property. Aconsistency property includes two parts: (1) a property name such asaccess and (2) a set of classifications, such as name, idy, and race.Given the consistency properties defined by an application developer, anatural question to ask is how will the application deployer use them.An application deployer first queries the application for allapplication-defined properties. Next, the application deployerassociates roles to consistency properties. Suppose an applicationdeployer defines two roles called Manager and NonManager, and associatesthe Manager role with access(name,idy,race) and NonManager role withaccess(name). With this association, a Manager can access all thedefined fields, whereas a NonManager can only access the fields fnameand lname. Notice that a deployer does not need to understand how adeveloper defined the consistency properties. The deployer only has toknow what set of consistency properties have been defined by thedeveloper.

Role Typestates: RBAC's are defined by focusing on the typestateconsistency property. The approach that may be employed is very simple:an application developer defines the typestate properties and anapplication deployer then assigns roles based on the typestateproperties. Typestates provide much richer information than simplemethod interfaces to an application deployer.

The concept of a typestate may be understood as an extension to thenotion of a type by providing that a variable be in a certain statebefore operations on the variable can be performed. In other words,certain preconditions have to be met prior to performing any operationon a variable. Typestate is useful for tracking certain kinds offlow-sensitive errors or bugs, such as uninitialized variables. Forobject-oriented (OO) programs, the typestate of an object (that is, aninstance of a class) is a description or a configuration of all itsfields. In OO programs, a method that is invoked on an object otypically has a partial view of the object o. One can use typestates todefine a consistent view of an object prior to an invocation of a methodon the object. Consider a simple file object that includes twotypestates Open and Close.

File Object with Two Typestates:

 class File  { typestate =  Start, Open, Close // @requires Start Filecreate(String fname)  ;  // create file // @requires Close void open( ) // // @requires Open String read( )  ;  // returns the content of file// @requires Open void write(String data)  ;  // write to file //requires Open void close( )  ;  // close the file }

Referring to FIG. 7, a typestate diagram is a finite state diagram, withnodes denoting the typestates of a class (e.g., open and close) and alabeled edges denoting transitions between typestates of a class. Thelabels on the edges (e.g., close( ), open( ), create( ), read( ), write()) correspond to (a subset of) methods defined in the class. The sourceand destination nodes of a transition correspond to pre- andpost-conditions of the method that labels the transition, respectively.An execution of a method takes an instance of a class from one typestateto another typestate. FIG. 7 illustrates a typestate diagram for theFile class code (FILE OBJECT WITH TWO TYPESTATES) presented earlier. Thetypestate diagram specifies the life-cycle of how an instance of theFile class goes between Open and Close typestates. A method, such asopen( ), is executed only when its pre-condition typestate of the Fileobject is Close, and after the execution the new typestate of the objectis Open. Both read( ) and write( ) methods can execute only when theFile object is in Open state.

The typestate diagram is an external specification of a class. Itprescribes the order in which a client can invoke various methodsdefined in the class. Generally, only an application developerunderstands the lifecycle of an object. Given such a specification, anapplication deployer can now associate security properties totypestates. For instance, an application deployer can associate Managerrole to Start, Open and Close typestates, and Engineer role to Open.What this essentially means is that only a Manager is permitted toexecute all methods of the class, whereas an Engineer is permitted toexecute only read( ) and write( ) methods.

In accordance with present principles, a typestate diagram may bepartitioned into a hierarchical structure and use the notion of ahierarchical typestate diagram. A hierarchical typestate diagramincludes a set of states and a set of transitions. A state may becomposed of other states, called sub-states. This enables modeling of acomplex hierarchical typestate diagram by abstracting away detailedbehavior into multiple levels. States that do not include sub-states arecalled simple states, whereas states that have sub-states are calledcomposite states. States may be nested to any level. A transitionrelates two states: a source state and a destination state. Transitionsare labeled and each label corresponds to a method invocation. Aninvocation of a method can cause a state transition. The hierarchicalstates in a typestate diagram may induce a tree structure. FIG. 8illustrates a hierarchical typestate diagram in which the Open stateshown in FIG. 7 has been expanded. For role typestates, it is natural tomodel roles using a tree structure.

Referring to FIG. 9, a tree structure 120 having role assignments modelsis illustratively shown. Roles R0-R4 are assigned to each method in thetree. The definition of senior relation is simpler: r

 s if r is a parent of s in the role hierarchy tree 120. Roles areassigned to hierarchical states in the typestate diagram. If s isassigned the role r then the Per(r)={t|tεRoot(s)}, where Root(s) is aset of all states in the sub-tree that is rooted at s in the typestatehierarchy tree 120.

Consider the role assignment shown in FIG. 9, and the permission set foreach role includes:

Per(R0) = {File,Open,Close,OpenRead,OpenWrite}, Per(R1) ={Open,OpenRead,OpenWrite}, Per(R2) = {Close}, Per(R3) = {OpenRead}, andPer(R4) = {OpenWrite}.

If a principal P is assigned the role R1 then P can invoke both read andwrite, but cannot invoke close. Now if P is assigned R3 then P can onlyinvoke the read method.

Consider a method such as File.close( ) and a principal P who isassigned the role R1. The principal P should not be allowed to invokeFile.close( ) even if the current typestate of the object referenced bythe principal is Open. This is because, the method File.close( ) createsa state transition from Open to Close and P is not allowed to be instate Close. So only principals with role File are essentially permittedto execute File.close( ).

Given a set of roles assigned to typestates, the roles needed formethods can easily be computed as the least common ancestor of the rolesassigned to the pre- and post-state of the method. Note that when a Fileobject is passed around to different methods that are accessed bydifferent principals, we only have to ensure that roles are consistenton the current typestate of the object and do not have to worry aboutthe methods themselves.

Typestates are useful for modeling access patterns, including messagepatterns in, e.g., Web Services. Once such message patterns are modeledusing typestates, roles can be assigned to states using the presentprinciples and provide security for applications, e.g., Web Serviceapplications.

The present embodiments address the challenges of role assignment androle semantics in building applications. The prior art method-basedaccess control is limiting in terms of its expressive power. Inaccordance with one embodiment, a data-centric security is employed tocomplement the method-based security. Role-based access control formanaging and controlling access to sensitive resources is provided. RBACmodels have become popular because of their generality in expressing adiverse set of access control policies. Security analysis techniques areprovided for ensuring that security properties are correctly maintainedeven in the presence of delegating administrative privileges.

A simpler lattice structure for modeling roles is also employed. Thenotion of role escape analysis is introduced to specially address theneed for data-centric security. Also presented is consistency-basedsecurity, along with role typestates for specifying access controlsecurity.

The role analysis described herein is related to static analysis. Theconsistency-based security and role typestate is one preferred way toextend the J2EE™ model to deal with data-centric security.

Java 2 Standard Edition™ (J2SE™) provides security mechanisms forprotecting resources (e.g., the file system) in terms of run-time stackinspection. The security access control model is based on propertiesthat include code origin and principals execution environment. Thepresent disclosure follows program analysis techniques for RBAC, usestypestate properties for RBAC, and introduces the notion of role escapeanalysis and the notion of role typestates to model and detect securityproblems, e.g., in J2EE™.

In accordance with present principles, role escape analysis generalizesthe traditional escape analysis, where the method and thread lifetimeare considered to be an instance of roles. Role escape analysis isuseful for detecting confinement properties of objects, and fordetecting information leaks through objects.

Role typestates combine the notion of roles and typestates. Byassociating roles to typestates, a more general model is defined forspecifying roles; instead of specifying roles on methods, the role arenow specified on typestates.

The present disclosure describes some of the security issues related toJ2EE™ RBAC model, illustrated several examples that show the limitationof method-based role assignment, and discussed the concepts that bringout a data-centric security model. Consistency based security thatincludes typestate security may be employed to complement method-basedsecurity. In other words, the present principles may be employed inaddition to or instead of the security measures employed in the priorart environments.

Referring to FIG. 10, a block/flow diagram showing a system/method forproviding access control using roles is illustratively depicted. Inblock 202, for at least one typestate, typestate properties aredetermined or provided. In one example, typestate properties include anassociation of a security property (or level) with the typestate toassign the role to the typestate.

In block 204, a role is assigned to the at least one typestate in aprogram in accordance with the typestate properties. In block 206, atypestate hierarchy tree may be generated and roles are assigned tonodes of the hierarchy tree where the nodes represent the typestates.

In block 210, access to operations of the at least one typestate in theprogram are limited based on the role assigned to the at least onetypestate and an access permission level. Limiting access may includedenying access to the at least one typestate if a role is junior to anassigned role and/or permitting access to the at least one typestate ifa role is senior to an assigned role.

In block 212, a role consistency analysis may be performed to determineif assigning the role is consistent throughout the program. In block214, a role escape analysis may be performed to determine if any programobjects escape a role assignment. In block 216, a method-based accesscontrol method may be employed instead of or in addition to the presentmethod for access control.

Referring to FIG. 11, a block/flow diagram showing a system/method foranalyzing role consistency for program access control is illustrativelydepicted. In block 302, for each object in a program having a pluralityof objects, a set of methods that directly access an object is computed.This may include generating a pointer graph of the program, such as, amethod-annotated pointer graph.

A role assignment is checked for each object by determining if theobject's role is a least upper bound of the roles assigned to themethods of the set in block 304. Access is permitted to the set ofmethods if an accessor's role is at least equal to the least upper boundof the roles assigned to the methods that access the object in block308.

A role escape analysis (blocks 320-324) may be performed instead of orin addition to the role consistency analysis (blocks 302-308) todetermine if any program objects escape a role assignment. The roleescape analysis includes constructing a pointer graph for a programhaving a plurality of objects having assigned roles in block 320. Inblock 322, each object O is checked to determine if O role escapes arole R by determining if there exists another path to that object O inthe pointer graph that can be reached by some node O′ that is accessedin another role R′ and a lifetime of the method R′ exceeds the life timeof R. In block 324, it is determined whether information is leaked orcontained based upon role escaped objects or lack thereof. The roleconsistency analysis may be performed separately or in addition to therole escape analysis.

Referring to FIG. 12, an illustrative system 400 includes a programaccess control program or module 402 capable of supporting role-basedsecurity and role-based security compliance in accordance with thepresent principles. Program 402 is preferably incorporated into theoperating system of computers, nodes and servers where access control isneeded. In one embodiment, each operating system for all devicesemployed in the system 400 employs the role-based system of the presentinvention. System 400 may include a private computer network, a singlecomputer (409) or a public computer network, such as the Internet or anycombination of these. In addition, the role-based access control may beemployed in telephones (cell phones), handheld or laptop computers(e.g., PDAs), or any other computing device or system.

Server 401, computer 409 and each computer or node 404 in the networkmay include memory storage 403 (e.g., RAM) where an operating system 405in conjunction with a processor 407 and communication protocols areemployed to facilitate communications between network or computer usersand perform the action needed for access control in accordance withpresent principles. Nodes or computers 404 may include access points fora plurality of users to a server 401 or may include individual computerswhich grant or deny permission to gain access to methods 406 and/ortypestates 408 stored on a computer or server 401. Although methods 406and typestates 408 are shown in the server 401 and computer 409, any orall computers 404 in the network or independent computers 409 mayinclude methods and typestates that are under access control. Themethods and typestates include roles such that a principal attempting toaccess the method and/or the typestate can gain access to the method ortypestate only if the proper permission or access level in afforded tothat principal. By employing typestates and other principles disclosedherein, method-based access control is extended by moving to a moredata-centric access control system.

Program 402 may be distributed over the network or located on a server;however, program or module 402 is preferably included in the operatingsystem of individual computers or servers. Program 402 further includesfeatures to provide for role assignment, check for role consistency anddetermine whether any roles assigned can be escaped as described abovein accordance with present principles.

Having described preferred embodiments of a system and method for rolebased analysis and access control (which are intended to be illustrativeand not limiting), it is noted that modifications and variations can bemade by persons skilled in the art in light of the above teachings. Itis therefore to be understood that changes may be made in the particularembodiments disclosed which are within the scope and spirit of theinvention as outlined by the appended claims. Having thus describedaspects of the invention, with the details and particularity required bythe patent laws, what is claimed and desired protected by Letters Patentis set forth in the appended claims.

1. A method for program access control, comprising: for at least onetypestate, providing typestate properties; assigning a role to the atleast one typestate in a program in accordance with the typestateproperties; and limiting access to operations of the at least onetypestate in the program based on the role assigned to the at least onetypestate and an access permission level.
 2. The method as recited inclaim 1, further comprising generating a typestate hierarchy tree andassigning roles to nodes of the hierarchy tree wherein the nodesrepresent typestates.
 3. The method as recited in claim 1, whereinproviding typestate properties includes associating a security propertywith the typestate to assign the role to the typestate.
 4. The method asrecited in claim 1, further comprising performing a role consistencyanalysis to determine if assigning the role is consistent throughout theprogram.
 5. The method as recited in claim 1, further comprisingperforming a role escape analysis to determine if any program objectsescape a role assignment.
 6. The method as recited in claim 1, whereinlimiting access to operations includes denying access to the at leastone typestate if a role is junior to an assigned role.
 7. The method asrecited in claim 1, wherein limiting access to operations includespermitting access to the at least one typestate if a role is senior toan assigned role.
 8. The method as recited in claim 1, wherein themethod is included with and extends a method-based access controlmethod.
 9. A method for analyzing role consistency for program accesscontrol, comprising: computing, for each object in a program having aplurality of objects, a set of methods that directly access an object;checking a role assignment for the object by determining if the object'srole is a least upper bound of the roles assigned to the methods of theset; and permitting access to the set of methods if an accessor's roleis at least equal to the least upper bound of the roles assigned to themethods that access the object.
 10. The method as recited in claim 9,wherein computing includes generating a pointer graph of the program.11. The method as recited in claim 10, wherein pointer graph includes amethod-annotated pointer graph.
 12. The method as recited in claim 9,further comprising performing a role escape analysis to determine if anyprogram objects escape a role assignment.
 13. A computer program productcomprising a computer useable medium having a computer readable program,wherein the computer readable program when executed on a computer causesthe computer to analyze role consistency for program access control asrecited in claim
 9. 14. A method for analyzing role consistency forprogram access control, comprising: constructing a pointer graph for aprogram having a plurality of objects having assigned roles; checkingeach object O to determine if O role escapes a role R by determining ifthere exists another path to that object O in the pointer graph that canbe reached by some node O′ that is accessed in another role R′ and alifetime of the method R′ exceeds the life time of R; and determiningthat information is leaked based upon role escaped objects.
 15. Themethod as recited in claim 14, further comprising performing a roleconsistency analysis to determine if assigning the role is consistentthroughout the program.
 16. A computer program product comprising acomputer useable medium having a computer readable program, wherein thecomputer readable program when executed on a computer causes thecomputer to analyze role consistency for program access control asrecited in claim
 14. 17. A computer program product comprising acomputer useable medium having a computer readable program for programaccess control, wherein the computer readable program when executed on acomputer causes the computer to perform the steps of: for at least onetypestate, providing typestate properties; assigning a role to the atleast one typestate in a program in accordance with the typestateproperties; and limiting access to operations of the at least onetypestate in the program based on the role assigned to the at least onetypestate and an access permission level.
 18. The computer programproduct as recited in claim 17, further comprising performing a roleconsistency analysis to determine if assigning the role is consistentthroughout the program.
 19. The computer program product as recited inclaim 17, further comprising performing a role escape analysis todetermine if any program objects escape a role assignment.
 20. Thecomputer program product as recited in claim 17, wherein limiting accessto operations includes at least one of denying access to the at leastone typestate if a role is junior to an assigned role and permittingaccess to the at least one typestate if a role is senior to an assignedrole.